INVESTMENT OPERATIONS - Summary of Change in Unrealized Gains (Losses), Net of Income Tax, on Fixed Maturity and Equity Securities, Classified as Available-for-Sale (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Fixed maturities
Investment Holdings [Line Items]
Change in unrealized gains (losses), net of income tax	$ 1,310,979	$ (229,912)	$ 4,410,162	$ (1,735,210)